LIM‐only protein FHL2 regulates experimental pulmonary Schistosoma mansoni egg granuloma formation

Abstract

LIM-only protein FHL2 is associated with several immune and inflammatory diseases such as arthritis, influenza A virus infection, and lung inflammation. However, the role of FHL2 in macrophage differentiation and in the development of granuloma formation is unknown. Here, we show that expression of FHL2 is induced in mouse bone marrow derived macrophages (BMMs) following stimulation with M2 cytokines such as IL-4 and IL-10. FHL2-knockout (FHL2-KO) BMMs exhibit a proinflammatory M1 phenotype after LPS treatment and display a reduced anti-inflammatory M2 phenotype following IL-4 treatment. Furthermore, thioglycollate-induced migration of macrophages and B cells is enhanced in FHL2-KO mice. To evaluate the importance of FHL2 in the development of pulmonary granuloma formation, FHL2-KO mice were challenged with Schistosoma mansoni eggs. FHL2-KO mice show an enhanced number of granulomas and display decreased expression of Th2 markers and an exacerbated Th1 type of inflammation, characterized by enhanced expression of neutrophil markers and Th1 cytokines. Furthermore, the expression of barrier proteins is reduced in FHL2-KO lung compared to WT. Collectively, these data identify a previously unrecognized role for FHL2 in the pathogenesis of pulmonary granulomatous inflammation, partly through its effect on macrophage polarization, modulation of the Th1/Th2 balance and regulation of permeability in lung. Keywords: FHL2 granuloma Macrophages Permeability Schistosoma mansoniAdditional supporting information may be found in the online version of this article at the publisher's web-site IntroductionThe helminth parasite, Schistosoma mansoni (Sm) causes some of the most debilitating and chronic diseases of mankind affecting Correspondence: Prof. Carlie J.M. de Vries e-mail: c.j.devries@amc.uva.nl more than 200 million people worldwide [1][2][3]. Schistosomiasis is a chronic disease that persists for years because of impaired ability to remove adult worms and the eggs that become trapped in the liver, lungs, and intestine as well as inadequate repair of local cellular damage [4]. Infection by Sm involves distinct phases, including an initial Th1 response involving IFN-γ followed by a stronger Th2 response, reflected by excessive expression of IL-4, IL-5, and IL-13, resulting in recruitment and activation of dendritic cells, C 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu Eur. J. Immunol. 2015. 45: 3098-3106 Immunity to infection 3099 eosinophils, Th2 cells, and alternatively activated macrophages or M2 macrophages [3,5]. Macrophages are a heterogeneous population of immune cells playing a crucial role in the regulation of both innate and adaptive immune responses in inflammatory diseases, such as airway inflammation, inflammatory bowel disease, and atherosclerosis [6]. Macrophage polarization is a key event in multiple chronic pulmonary diseases including schistosomiasis and may help in regulation of tissue repair. Classical activation of macrophages (often indicated as M1) is induced by IFN-γ or LPS ...

The role of FHL2 in wound healing and inflammation

“…Kurakula et al (61) also reported that the Th2 response was decreased in FHL2-KO lungs inflamed by Schistosoma mansoni eggs in comparison with the infected lungs of WT mice. This was accompanied by an enhanced expression of neutrophil markers and Th1 cytokines (49), but the infiltration of lungs by immune cells was not analyzed in this study. A decreased infiltration and activation of neutrophils and NK cells into the lungs of FHL2-KO mice after S. pneumoniae infection led to an increased bacterial burden and lung tissue damage as shown by Baranek et al (50).…”

“…A more controversial picture appears while analyzing published data regarding proinflammatory cytokine expression by macrophages upon LPS stimulation. Induction of TNF-a and IL-6 cytokines in FHL2-KO macrophages compared with WT cells varied from being enhanced (33) to reduced (49) or not affected (25), depending on the report. It must be mentioned that the source of macrophages as well the longevity of LPS stimulation were always different in these studies, implicating again the cellular background and surrounding conditions as critical in FHL2-controlled expression of proinflammatory cytokines.…”

“…The role of FHL2 in the clearance of pathogens other than the influenza virus has also been studied. It was reported that FHL2-KO mice were impaired in the elimination of helminth eggs from murine lungs because of an imbalanced T helper (T h )1 and T h 2 cytokine production, which finally led to the formation of pulmonary granulomas (49). Also, clearance of Streptococcus pneumoniae was shown to be disturbed in the lungs of FHL2-KO mice because of a deficient function of NK cells and neutrophils.…”

Role of Macrophages in the Repair Process during the Tissue Migrating and Resident Helminth Infections

“…To prove the importance of FHL2 in AAM activation, FHL2 −/− mice were challenged with S. mansoni showing higher numbers of granulomas and reduced expression of AAM markers, which correlate with an enhanced Th1 immune response. These data suggest a role for FHL2 in the pathogenesis of pulmonary granulomatous inflammation through AAM polarization and Th1/Th2 balance [62]. …”

LIM-only protein FHL2 attenuates vascular tissue factor activity, inhibits thrombus formation in mice and FHL2 genetic variation associates with human venous thrombosis

“…HEK293T, human umbilical vein endothelial cells (HUVEC), murine and human SMC, and murine macrophages were cultured as described previously. [28][29][30]33,34 Human microvascular endothelial cells (HMEC-1) were cultured in MCDB131 medium (Gibco, Blijswijk, the Netherlands) supplemented with 10% fetal calf serum, epidermal growth factor, penicillin/streptomycin, and Lglutamine. The human endothelial cell line ECRF was cultured in EGM2 medium (Lonza, Basel, Switzerland).…”